yes, i know - that question has thousands of answers. please, don't tell me about "setTimeout" method becasuse - yes, everything is possible with that but not so easy as using sleep() method. for example: function fibonacci(n) { console.log("Computing Fibonacci for " + n + "..."); var result = 0; //wait 1 second before computing for lower n sleep(1000); result = (n <= 1) ? 1 : (fibonacci(n - 1) + fibonacci(n - 2)); //wait 1 second before announcing the result sleep(1000); console.log("F(" + n + ") = " + result); return result; } if you know how to get the same result using setTimeout - tell me ;) fibanacci is pretty easy task, because there not more than 2 recursions, but how about n-recursions (like fib(1) + fib(2) + .. + fib(n) and sleep after every "+"? nah, sleep would be muuuuuch easier. but still i can't get working example of implementing it. while (curr - start < time) { curr = (...) } is tricky, but it won't work (just stops my browser and then throw all console.logs at once).